/**
 * Copyright (c) 2012-2017, www.tinygroup.org (luo_guo@icloud.com).
 * <p>
 * Licensed under the GPL, Version 3.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * <p>
 * http://www.gnu.org/licenses/gpl.html
 * <p>
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.tinygroup.jspengine.runtime;

import org.tinygroup.jspengine.security.SecurityUtil;

import javax.el.FunctionMapper;
import java.lang.reflect.Method;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.security.PrivilegedActionException;
import java.security.PrivilegedExceptionAction;
import java.util.HashMap;

/**
 * Maps EL functions to their Java method counterparts.  Keeps the
 * actual Method objects protected so that JSP pages can't indirectly
 * do reflection.
 *
 * @author Mark Roth
 * @author Kin-man Chung
 */
public final class ProtectedFunctionMapper extends FunctionMapper {

    /**
     * Maps "prefix:name" to java.lang.Method objects.
     */
    private HashMap fnmap = null;

    /**
     * If there is only one function in the map, this is the Method for it.
     */
    private Method theMethod = null;

    /**
     * Constructor has protected access.
     */
    private ProtectedFunctionMapper() {
    }

    /**
     * Generated Servlet and Tag Handler implementations call this
     * method to retrieve an instance of the ProtectedFunctionMapper.
     * This is necessary since generated code does not have access to
     * create instances of classes in this package.
     *
     * @return A new protected function mapper.
     */
    public static ProtectedFunctionMapper getInstance() {
        ProtectedFunctionMapper funcMapper;
        if (SecurityUtil.isPackageProtectionEnabled()) {
            funcMapper = (ProtectedFunctionMapper) AccessController.doPrivileged(
                    new PrivilegedAction() {
                        public Object run() {
                            return new ProtectedFunctionMapper();
                        }
                    });
        } else {
            funcMapper = new ProtectedFunctionMapper();
        }
        funcMapper.fnmap = new java.util.HashMap();
        return funcMapper;
    }

    /**
     * Creates an instance for this class, and stores the Method for
     * the given EL function prefix and name. This method is used for
     * the case when there is only one function in the EL expression.
     *
     * @param fnQName    The EL function qualified name (including prefix)
     * @param c          The class containing the Java method
     * @param methodName The name of the Java method
     * @param args       The arguments of the Java method
     * @throws RuntimeException if no method with the given signature
     *                          could be found.
     */
    public static ProtectedFunctionMapper getMapForFunction(
            String fnQName, final Class c,
            final String methodName, final Class[] args) {
        java.lang.reflect.Method method;
        ProtectedFunctionMapper funcMapper;
        if (SecurityUtil.isPackageProtectionEnabled()) {
            funcMapper = (ProtectedFunctionMapper) AccessController.doPrivileged(
                    new PrivilegedAction() {
                        public Object run() {
                            return new ProtectedFunctionMapper();
                        }
                    });

            try {
                method = (java.lang.reflect.Method) AccessController.doPrivileged
                        (new PrivilegedExceptionAction() {

                            public Object run() throws Exception {
                                return c.getDeclaredMethod(methodName, args);
                            }
                        });
            } catch (PrivilegedActionException ex) {
                throw new RuntimeException(
                        "Invalid function mapping - no such method: "
                                + ex.getException().getMessage());
            }
        } else {
            funcMapper = new ProtectedFunctionMapper();
            try {
                method = c.getDeclaredMethod(methodName, args);
            } catch (NoSuchMethodException e) {
                throw new RuntimeException(
                        "Invalid function mapping - no such method: "
                                + e.getMessage());
            }
        }
        funcMapper.theMethod = method;
        return funcMapper;
    }

    /**
     * Stores a mapping from the given EL function prefix and name to
     * the given Java method.
     *
     * @param fnQName    The EL function qualified name (including prefix)
     * @param c          The class containing the Java method
     * @param methodName The name of the Java method
     * @param args       The arguments of the Java method
     * @throws RuntimeException if no method with the given signature
     *                          could be found.
     */
    public void mapFunction(String fnQName, final Class c,
                            final String methodName, final Class[] args) {
        java.lang.reflect.Method method;
        if (SecurityUtil.isPackageProtectionEnabled()) {
            try {
                method = (java.lang.reflect.Method) AccessController.doPrivileged(new PrivilegedExceptionAction() {

                    public Object run() throws Exception {
                        return c.getDeclaredMethod(methodName, args);
                    }
                });
            } catch (PrivilegedActionException ex) {
                throw new RuntimeException(
                        "Invalid function mapping - no such method: "
                                + ex.getException().getMessage());
            }
        } else {
            try {
                method = c.getDeclaredMethod(methodName, args);
            } catch (NoSuchMethodException e) {
                throw new RuntimeException(
                        "Invalid function mapping - no such method: "
                                + e.getMessage());
            }
        }

        this.fnmap.put(fnQName, method);
    }

    /**
     * Resolves the specified local name and prefix into a Java.lang.Method.
     * Returns null if the prefix and local name are not found.
     *
     * @param prefix    the prefix of the function
     * @param localName the short name of the function
     * @return the result of the method mapping.  Null means no entry found.
     **/
    public Method resolveFunction(String prefix, String localName) {
        if (this.fnmap != null) {
            return (Method) this.fnmap.get(prefix + ":" + localName);
        }
        return theMethod;
    }
}

